// Copyright 2016 Sorint.lab
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied
// See the License for the specific language governing permissions and
// limitations under the License.

package postgresql

import (
	"encoding/binary"
	"os"
	"path/filepath"
	"strconv"
)

func (p *Manager) GetSystemdID() (string, error) {
	pgControl, err := os.Open(filepath.Join(p.dataDir, "global", "pg_control"))
	if err != nil {
		return "", err
	}
	var systemID uint64
	err = binary.Read(pgControl, binary.LittleEndian, &systemID)
	if err != nil {
		return "", err
	}
	return strconv.FormatUint(systemID, 10), nil
}
